1. Field of the Invention
The present invention relates to high specific energy batteries having an alkali metal, preferably lithium, as a negative active material and relates particularly to a positive active material for such a battery.
2. Discussion of the Prior Art
Since at least 1960 it has been proposed to use oxides of lead as the positive active material for batteries in which the negative active material is lithium, among others. See, for example, U.S. Pat. No. 2,937,219 issued to L. J. Minnick et al. on May 17, 1960. More recently, U.S. Pat. No. 4,018,970, issued to Yves Jumel et al. on Apr. 19, 1977, and commonly assigned with this application, has described lithium batteries of which the positive active material is composed of lead oxides having the formula PbO or Pb.sub.3 O.sub.4. The disclosure of the latter patent is incorporated herein by reference.
It would be desirable, however, to use lead peroxide, PbO.sub.2, as a positive active material because it has a theoretical specific capacity that is higher than that of Pb.sub.3 O.sub.4 and even more superior to that of PbO. Lead peroxide has also been proposed as a positive active material in the above-mentioned Minnick et al. U.S. Pat. No. 2,937,219. However, lead peroxide has the disadvantage of discharging over two steps or levels, which is an inconvenience in many cases.